Preventing cap walk

Just thinking out loud: could you prevent cap walk with roll pins drilled into the parting line between block and cap (parallel to cap bolts)?

I think the root cause of cap walk is a block that can not handle the power being generated. Most of the OEM muscle car blocks were designed to handle around 400HP, so what happens when you push something twice its designed capacity? A block girdle will help some, as does block filler, but they are just bandaids.

https://www.carshopinc.com/product_info.php/products_id/66507/M3840C4

Anyone try these 4 bolt mains caps?

Turn the timing back. It’s cheaper and easier.

I’m not sure how quick you want to go but sometimes we over think things. I’ve gone 8.60’s with 440 blocks and 9.70’s with 360 blocks with no bandaids. Did I have a little cap walk, sure I had some. If I wanted to do a quick stock block 440 again I would put main studs and aluminum caps on it and go racing. Save up your money and get a good block. I did.

I've even see some guys put bushings around the main studs to help prevent cap walk. it helps some, aluminum main caps on a big block are your number one add on that give you your best bang for your buck. cross bolt caps weaken the block because you have to remove the main webbing that's holding block together.

I keep mine at 34* so it doesn't detonate because that is what kills ANY engine

Gus

A man just needs to know his limitations........

In other words if the block you have isn't working for you then upgrade to a better block. If you are going to use a stock block in your project then stay within the limitations of the stock block. You should be able to build a very reliable 600 hp big block engine without having to mess with any bandaids. If you need more than that then either take your chances or step up.

I've found that detonation and poor tuning lead to cap walk even on low compression(less than 9.5 to 1 with iron heads) street engines that make power above 500 HP
I disagree on using the girdles and block filler
Not good having cement block filler due to having two different heat ranges in the cylinder walls causing block distortion around the cylinder walls
On using the current after market girdles when you look at the BB Mopar and FE Ford designed blocks that have the main webbing support ribs in the block starting down low around the oil pan rail going up to the upper main bearing webbing using a main girdle that uses the stock 5/16 size oil pan bolts does nothing to strengthen the blocks, does it
Replace the stock main caps and use main studs and spend the left over money on better parts in the stock blocks
Or better yet do as AndyF suggest, get a better block

You got it Pittsburgh. Main studs and aluminum main caps. As for those 1/4" thk. main girdles, not even a good band-aid.

Early 360, over 500HP, block filler, under 12:1, good gas, 38 degrees, ARP studs, and they stilled showed fretting. RPM plays into this a great deal.

Aluminum caps don't prevent cap walk. (not saying they aren't a good replacement for cast iron) Aluminum just doesn't allow the transfer of material at the mating surface, so there is no evidence of it. If you see peppering on the mating surfaces, you are running to much ignition advance at some point in your curve. Early timing tries to hammer the crank out of the bottom, lifting and distorting the caps. Delay the ignition and the crank rolls forward....
There is a whole lot more power potential in a factory big block than most think. Just have to treat it right.

My understanding:

Aluminum caps absorb the "shocks" so the caps shouldn't bounce around as much as iron/steel. Maybe it was Monte Smith who used the analogy of hitting something with a dead-blow hammer vs a standard hammer that doesn't absorb the hit.

Most girdles aren't expected to strengthen the block; the benefit is tying the main caps together to keep them better aligned as a unit when the rotating assembly is trying to push them all in different directions.

It's funny (to me) when there always seem to be people who p!ss on one approach or the other, since I see benefits to using them both together.

I look at teing the main studs together with the girdle as a bad thing due to the girdle trying to flex the studs, main caps and block as the firing order occurs Not a good thing, huh
Good intentions, designing producing and selling the girdle systems, don't always produce good results

Maybe not always, but there are some good running stock block strokers out there 1/2 filled and chastised. Pretty damn reliable ones too!

I agree with this cab. Every time I used a girdle the main bearings looked bad and finally we came to the conclusion that the girdle was actually moving stuff around.

And, most of the time, especially with fairly agressive lobes, you can take a stud girdle off a Chevy and they will make more power. The motion of the valve is translating all its business to other valves that shouldn't be moving.

The valve job seemed to last longer and look better on freshen up.

Tell me again how a plate with 22 odd bolts in it is flexing a 300,000 psi stud?

That's another thought I had: drill out the bolt hole in the block and cap a bit so that a bushing/sleeve can be fitted over the studs that extends into the block and cap.

Thanks for all the replies! Not that I'm having cap walk or plan to build an 800hp engine My question was just out of curiosity from an engineering standpoint: if such a simple solution with roll pins could help if someone (not particularly me) is experiencing cap walk.

Cross bolting weakens a stock block and still doesn't stop them from "walking". I remember seeing pictures on here of a Megablock that had some bad cap walk issues.

I don't think dowel pins would do much. The caps bounce, not necessarily moving them back and forth.

Just my opinion...I'd use aluminum caps and stud it.

All you can do for a stock block deal is run a center weighted crank with light bob weight, use studs and aluminum caps on a bb. Look at the new Ford Coyote blocks to see what it takes to keep everything from moving around too much. And they START with a center weighted crank!

I have built several BB Mopar engines in the last 10 years and am well aware of what cap walk is and what it looks like on the mating surface of the main caps and block registers. I have incorporated the 1/4" girdle on the past 6 builds and can tell you that the two that I have had apart with a girdle in place have ZERO signs of cap walk. My 505 RB produces a little over 600 horsepower and was one of the two I took apart for a refresh after 12,000 hard miles.
With no affordable aftermarket blocks available in the near future, I really don't see the downside of using ANY device that can help prevent a 40 plus year old stock block that was NOT designed to handle the power levels that can be achieved with aluminum heads and roller cams from going BOOM !!!!
If you want the ultimate setup for a stock block you should call Jerry at BCR Products. His girdle and aluminum cap design is as good as it gets.

Common guys, get out of the past and accept new ideas. I promise it won't hurt

As long as it doesn't bust the block or knock the mains out, who cares? Again it all goes back to controlling detonation. You can only control what you can control. Sure a KB block and Bryant center weighted crank will help. Just not in everyone's budget.
Doug

Part of this debate has me scratching my head. The girdle doesn't move, everything else does. So how can anyone imagine the girdle pushing a stud or main cap around if the stud or main cap weren't already moving?

We've talked about this before. When the engine is making max torque, the crankshaft is not remaining perfectly straight. It cannot help but move, since it has pistons and rods pushing or pulling on it in two major directions. If one could plot the path of a point on the outside of a counterweight it wouldn't describe a circle. I believe it'd have more of an egg shape.

The crank is flexing corresponding to how much force is being applied to it. This causes the main webs to tilt back and forth as the forces are transferred from the crank to the bearings to the block. The girdle helps to stabilize the main webs.

If installing a girdle results in the main bearings having excessive wear on their edges, then you know the girdle is holding the main webs pretty straight and the crank is flexing in the journal. To combat that one could use more crank overlap but this means larger diameter bearings. One could reduce the mass of piston and rod, because inertia forces exert a pull on the crank, flexing it. One could use a stiffer material but I don't have any idea what that'd be. Center counterweights seem to help because their effect is closer to the problem.

Adding dowels to the main caps would help because it puts the dowel pin in single shear. BUT, It needs to be calculated if that resistant force exceeds the friction between cap and block which is provided by the force exerted by a screw which would be installed instead of the dowel and torqued to 80% yield.

Remember that any metal must deform to carry a load.

R.

Same here. My current block has the Pro-Gram 4-bolt conversion caps, but I won't go that way again. The fresh block awaiting my next build has aluminum main caps, and will be paired with a CRE girdle I've had for years.

They're all Band-Aids when you're working with 40+ year-old blocks.

Keep timing in check, use as light a bobweight as you can AFFORD, a center counter weighted crank is a great upgrade to ANY performance engine, aluminum caps IMO are a good addition and cannot see a girdle HURTING anything. Bottom line is detonation will kill ANY block. You can stop the fretting of the cap material with a little anti seize but it does nothing to affect the root cause obviously. In the end build and run what you can afford.

By time you concrete fill a block, aluminum caps, girdle, and machine a block for the girdle how much money did you spend? And if you make any r al
Horsepower (not talking 600 horsepower here) it will crack sooner or later. I watched Tom Hemphill try ever trick in the book and when they were really leaned on and raced often there went a lot of wasted money that could have gone towards a good block. And don’t say there aren’t blocks out there because I know better.

Iv'e done this to myself before, so no judgement made on my part.

Spending tons on a stock block trying to hold it together to do what it was never intended to do. By the time I got where I was going anyway, I'd be dollars ahead just buying a real race oriented block.

I have some mega, and KB blocks that have center weighted bryants, or winberg, and they still show signs of fretting. So I've decided not to fret personally about it. The happiest people I know in racing, just pound away at their stuff, enjoy the ride, and repair, or rethink when effort, or budget interfere.

Not saying caution to the wind, just enjoy them more, than worry over them. Cap walk is hard to avoid when you're making power with them. The tune for sure is the greatest cause, but who has time to completely re tune every time the weather changes?

Is there a "best practice" engineering rule of thumb as to how much metal must be around and below a specific female thread?
Obviously, a 5/16-18 pan rail bolt can't just be re-tapped to 7/16-14 if it moves the thread to within 1mm of the edge of the rail, but how much is safe?
From photos, it looks like there's some room around the B pan bolts (and obviously the original is perfectly safe at its original torque specs).

Anyone familiar with a strap above the cap pre-loading it?
From a print source:
"This is not a substitute for a better cap, but it works very well – if you have the time and spares to test it. There are several methods. The caps can be pre-loaded by making the center of the strap (directly above the center of the cap arch) .002” deeper (not a suggestion, use your own judgment) than the remainder, or making it flat and inserting a .002” shim, thus compressing the cap arch when the strap is torqued into place. This helps to prevent the cap bearing bore from “ovalling” under high load & speed. This can be done by machining the strap, or simply using stand-offs .002” shorter than the contact distance. This distorts the caps, and requires line boring with the new parts installed.
Straps have been made with a large fine-pitch bolt (such as 1∕2-20 NF) threaded into the strap’s center, which, when torqued, exerts pressure down and acts as a jacking screw to pre-load the cap at the center of the arch.
Too little pre-load torque: all you did is waste your time and weaken the strap with the extra hole.
Too much pre-load torque: the cap distorts the main bearing, or cracks through the center of the arch."

the big difference between our bcr girdle kit and all the others is in our caps. if you look at the above posted pic. our caps are talled and contact the girdle below the crank. also the girdle is 1/2 thick steel. using stock caps or shorter caps, allows the cap to flex with the crank. we have a complete stack up of metal, the aluminum to help cushion the load and then the steel mated to the cap to reinforce the whole system.

our girdle caps are even better at helping distribute the load than the stock caps. they have a larger surface in contact with the girdle minimizing cap walk as much as possible with the stock block. we've even had guys do a half fill on their block with good success.

I agree however in the Mopar world there are more builds on the street and track using stock blocks making around 600 horsepower than aftermarket blocks making 800/1000 horsepower so a little extra help on a bottom end of a stock block is not a bad idea for the many as opposed to the few.
Wanna make real horsepower?? 800 to 1000?? Then yes, time to get out of the sand box, pry open the wallet and plan on spending some real money on a overpriced aftermarket Mopar block.
The reality is as time goes on there is less reason to produce aftermarket Mopar blocks due to the lack of demand so you may know better in that you are also aware of the warehouse in Flint that has 5000 cross bolt B blocks and 8000 RB blocks that will hit the market next Tuesday................

Get ready for GEN 3 blocks in your life if you like it or not.

I don't see how oversizing the mains where they thread into the block for a 9/16x12 (BB Ford?) or possibly a 5/8x11 stepped to a 9/16 (like the KB block) isn't a cheap solution...put a 440 source cap on it machine it all square and add power until the bores split. I'd have as much or more confidence in that than adding a girdle...JMO.

I'm at the point where my perspective is: "Whatever works for you, great... but don't p!ss in my Cheerios if you don't agree with my approach."

I have been 9 teens at 135? (cant remember exact MPH) with a .030 over 440. Stock block, stock caps (ARP studs and NOT line honed LOL), stock crank. Alum rods and 440-1 heads. Cant remember the exact nitrous amount but it got shot a lot...LOL. All that at 3600lbs..

Block is still good, but hey im sure it can let go at any time..LOL

Its all a matter of if you want to chance it and how lucky you are, some blocks let go right away, some last a lil while

haha ain't this the truth .
Personally like in other threads about similar stuff , I don't get why guys are over 600hp and want to race etc but wont stump up for better/stronger blocks . Cost is what it is and complaining won't make them cheaper . If you drive over your crank that aftermarket block will be cheap .


Tex

And sometimes driving over your crank results in more than just having to build a new motor...

And this is why guys should step up to the plate and put a diaper on their engine. They have saved more than one car from hitting the wall. Cheap insurance

now I should note I did try the stock block getting close to 700hp . When it split I decided I would not waste my money doing the same thing with attendant risks . I do have a stock block 440 , stock stroke , making around 570 or so . I believe this should last happily , been going 10 plus years .

Tex

I've determined the key to stock-block longevity is to never have an assembled engine in the car. But you may have to worry about the block rusting...

I've nothiced that cars driven to car shows and those that are only raced 3-4 times a year last a long time too. Almost ZERO cap-walk. My buddy has a built 454 chevy that is OVER 40 years old and he used to tell me about it every time he was drunk.

Long time doing these builds,have tried way to many combo's.
20 yrs ago,McCandless billet bridge stock cap system (6 1x1 notches in pan rail)
McCandless billet bridge with 3 pro-gram billet caps
McCandless aluminum caps
Indy aluminum caps
Pro-gram billet cross bolt conversion
Hughes girdle
Hughes girdle w/BCR aluminum caps
Full BCR girdle/aluminum cap system(which i believe is the best one for those that are desperate to hold on to a stock block(jury is out on this)
I comes down to the stock block foundation.
Simply ,its like trying to screw a sheet metal screw into a stick of butter.

My "new" block (machined, but not assembled) has Indy alum caps and a CRE girdle, which is basically the same as Hughes' girdle.

Ideal? Nope.

Paid for? Yep.

It'll have to do for a 650+ HP 3.75"-stroke 440.

Good use of words

Does anyone remember a magazine article yrs ago where they installed 1/2 inch cross bolts/studs in a hemi block (that I believe was cracked in the mains) and put 3/8 bolts with lock nuts through the pan rail to push down on the 6 cross bolts ???
Could have been like 30yrs ago.